Speaker and listening device



June 13, 1939. A, T. cAHlLL 2,161,995

SPEAKER AND LISTENING DEVICE Filed July 22, 1935 3 Sheets-Sheet l f l II`1 Z 545e 7a 910111215141015171319 zo June 13, 1939.

A. T. CAHILL 2,161,995

SPEAKER AND LISTENING DEVICE Filed July 22, 1935 s sheets-sheet 2 1715.230

A C akin June 13, 1939. A, T. cAHlLL SPEAKER AND LISTENING DEVICE FiledJuly 22, 1935 3 Sheets-Sheet 3 l lll Patented June 13, 1939 UNITEDSTATES PATENT OFFICE SPEAKER AND LISTENING DEVICE Arthur T. Cahill,

Application July 22,

4 Claims.

My present invention relates to improvements in what I Amay term radioeasy chairs, or rests for the body, in or on which the listener sits,reclines or lies comfortably, with his head near 5 one or between twospeakers, that are in prox- -i'mity to his ear or ears; that speak intothem softly or loudly as the listener desires; that yet do not producemuch sound, or 'at least too much sound, in the rest of the room; andthat, therefore, do not interfere with the work or play of other peoplein the room or in the rest of the house, as loud speakers now sofrequently do, and when I say a speaker or speakers, I mean to includeboth a speaker or speakers near to the 1 5 listeners ear or ears, or aspeaker or speakers at sonle distance therefrom, whose vibrations arebrought to the listeners ear or ears by a suitable tube or conductor orby suitable tubes or conductors, whose free end or ends are held adi.iustably near to the listeners ear or ears. Several constructions ofradio easy chairs are distclosed and claimed in the copendingapplication 'Of Thaddeus Cahill, Serial No. 660,667, filed March 14,1933, as a continuation of his application Serial No. 548,587, filedJuly 3, 1931, said copending application now having become Patent2,009,138, granted July 23, 1935.

The principal object of my invention is to produce an apparatus whichenables the listener to have all the volume of sound, speech or music hedesires without producing much sound in the rest of the room. This Iaccomplish preferably by putting the speakers in cases or shells, whichmay be of metal, *"a'kelte, hard rubber or any other Suitable material.The more sound deadening the material is the better for my purpose ofsuppressing vibration and so preventing the transmission of sound to theroom. Inside of the case, immediately forward of the vibrating cone 40or diaphragm, but not touching any of the Vibrating part of thediaphragm, is a casting or plate, preferably of metal so shaped andposiit'ioned with relation to the diaphragm as to direct toward alcentral outlet all the air moved by the 15 diaphragm or cone, andfinally to force out through a small orifice vibrations which are far'more intense than were the vibrations originally 'yproduced by thediaphragm itself. By such `means, I greatly increase or multiply theampli- 550 tude of vibration in the small stream of air delivered closeto or into, the ear or ears of the listener seated in my chair beyondthe amplitude of vibration of the diaphragm which initiated them. I havediscovered that the smaller the amplitude of i/ibratigga of thediaphragm is, fhg

Weehawken, N. J.

1935, Serial N0. 32,619

more perfectly it responds to the electrical vibrations which actuateit, and the less it introduces uncalled for vibrations on its ownaccount, as it is most prone to do when it vibrates intensely, and thatby my new invention I can cause the vibrations delivered to the ear orears of the listener in my radio chair to be of an intense, and,therefore, impressive character, although the diaphragm which initiatedthem may be vibrating only gently. Consequently, the sounds which Iproduce in the ears of a listener seated in one of my radio easy chairsare more perfect, truer, smoother and more beautiful than the sounds ofthe same Volumevibrations of the same amplitude-are, when produced by aloud speaker throughout the whole area of a room.

And I insulate my cases or shells carefully acoustically, with thicklayers of rubber, sponge rubber, cork, felt, or any other suitablevibration deadener or sound insulator.

It is highly important that this insulation cover all parts of theinside of the shell and be as airtight as is convenient so that no partof the inside of the shell be exposed to the aerial vibrations producedby the diaphragm, or to the physical vibrations of the speakersthemselves where they are clamped into the cases or shells, because ifany part of the shell is so exposed the vibrations will be transmittedto the shell and the vibrations of the shell will produce similarvibrations or soundsl in the room. One means of insulation which havefound very satisfactory is to have the rubber or the sponge rubbermolded right onto the inside of the snella-vulcanized to it-so coveringall parts of the inside of the shell and leaving no exposed surfaces ofthe eases or shells 'which vibrations can enter. In this way the soundtransmitted from the shells or cases is rendered almost whollynegligible and the only sounds to reach the outside air are the verysmall streams of highly concentrated vibrations which emerge from thesmiall central orices, and so are delivered near to, or directly towardthe ear or the ears of the listener. A sound which is thus delivered ina concentrated stream of intensified vibrations directly toward, andvery close to the ear, or ears of the listener need be only a very smallfraction of the sound which it is necessary for a loud speaker to makein order to lill the Whole room so as to produce an equal volume ofsound in the ears o f the listener. The result, with my invention 1S al'most total quiet in the room. In fact, lt 1s frequently diicult for aperson a few feet away, 09 i911 Whether or not any sound is beingproduced in the ears of the person seated in the chair, though thesounds may be very loud to the person in the chair. In this way theperson listening in the chair and the other people in the room, or inthe rest of the house, are about as independent of each other as if theywere in diiferent houses.

An important object of my invention is to so shape the air space betweenthe movable diaphragm and the vibration-limiting plate forward of thediaphragm, that the relatively small ampltude of vibrations over a largearea initiated by the diaphragm may be transformed into rela'- tivelyintense vibrations over a small area before they are delivered to theear of the listener, and to do this with the least possible loss ofpower, with constant and smooth acceleration, and without creating eddycurrents, distortions, or resonances.

Another object of my invention is to enable people whose hearing isdefective, to yet enjoy radio at their ease and without disturbing otherpeople in the same room, or in other parts of the same house, or eventheir neighbors. This I do by producing unusually powerful vibrations ofthe diaphragm and by delivering the highly concentrated and verypowerful resulting jets of vibratory air very close to (or even directlyinto), their ears.

Another object of my invention is to enable people whose hearing isquite defective, to again hear the speech and conversation of theirfamilies and friends. By the use of a microphone or microphones andamplifying devices, I pick up the speech vibrations in the room andamplify them greatly, and then, by feeding these amplified electricalvibrations to my speakers, and concentrating the resulting aerialvibrations through the specially-shaped air passages referred to,intensifying :them as above indicated, and delivering them near to ordirectly into the ear of the listener in the chair, I enable him to hearordinary conversation in the room-not merely words spoken directlyinto amicrophone, but also 'general conversation throughout the room. I

thus enable people who are hard of hearingeven the very hard ofhearing-to again enjoy family life and again. hear the Yconversations oftheir family andfriends, and, also, to conduct their regular business.

Anotherobject'of my invention is to 'improve the reception of telephonemessages. This I do by mounting one, or preferably two, speakers onanoicechain or desk chair (though any other suitable type of chair orsupport for the body may, of course, be used),`and connecting themwiththe telephone'lines. With two speakers attached to the chair in sucha position that when fthe user leans backiin the vchair his'head isbetween the speakers, see for example Fig. l, the

incomingtelephone'voiee will be spoken directly intohis ears-not a'whisper in one ear only, but

a loud, clear voice, and' talking into both ears. In other words, avoice'as loudand practically as clear as vif the'one telephoning tohimwere seated at hisside in'his oliice. This may be done by feeding'theincoming'telephone vibrations, directly or first through 'an `amplierdelsfirably having a volume control, `as mentioned below, into the.voice coils of the dynamic speakers, but is, of course, much betterdone, and is much louder and clearer' when the relatively lweakvibration overa large area is transformed into an intense vibration overa small area by my special speakers. And while theincoming under myconditions.

Vbackward Vand escape through voice may be many times as loud as it nowis, it will, on account of my acoustical sound suppressing devices, beinaudible to a person seated at the listeners elbownot nearly so audiblein fact as it frequently now is on the ordinary telephone, even thoughthe ordinary telephone voice is so much weaker. By this arrangement,when a man is working at his desk, leaning forward as he ordinarilydoes, his head is well away from, and entirely clear of the speakers.The instant the telephone rings, he simply leans back in his chair,which brings his head between the speakers above referred to, and swingsthe microphone, which is over at one side out of the way, in front ofhis mouth and proceeds with the conversation. Both his hands are leftfree for writing, for handling books, papers, price lists, discountsheets, or for the making of notes or the taking of orders, etc. With anordinary volume-control device in the circuit he can regulate theloudness of the sounds and make them just as loud or just as soft as hewishes, according to circumstances. The effect produced is far and awaybetter than in telephony today. About all the sounds we have ever heardexcept telephony, we have heard with both ears, and for easy, clear,natural hearing, and for full satisfaction, it seems necessary that thesound be produced in both ears. One ear does not fully satisfy and this.taken in conjunction with the feebleness of the ordinary telephoneVoice, is the cause, it is sub-- mitted, of the extreme nervousness ofmost people when they are using the telephone, a nervousl ness which isentirely absent from people using my chairs.

Another object of my invention is to reduce the cost of a combined radioeasy chair and a chair in which people whose hearing is quite defectiveYcan hear conversation in the room. This I do preferably by using a partof my radio set-the audio part of a radio set-as an ampliner for themicrophone voice, and so, without much `additional expense, -to have aradio easy chair, and also an easy chair for the deaf. My combined chairmay then serve as any easy chair for the deaf alone; that is to a chair,a speaker, an amplier with its necessary controls. and a microphone,in'which case radio could not be heard in it; a radio easy chair, whereno members of the family are hard of hearing; or a l combined radio easychair and a chair for the deaf, using a microphone and the latter stagesof the radio amplification, or a separate ampliner for the microphone.

Another object of my invention is to produce 'ing up'to a point, thoughof course right line angular sides may be used also, if desired. Thisdoes'away with the dead spot in the centre over the magnet which isinjurious in my work and They also work much better when used in regularloud speakers, because there is no dead spot in the centre. The wholearea of the cone moves forward as a piston and all the air enclosed orin front of it must move forward with it. Part cannot rush thespiderdown into the magnet or out around the voice coil. All the air must goforward and without any of the eddy currents or distortions which aredue to the dead spot over the magnet in ordinary cones. By properlyshaping and proportioning the vibrating cone and front piece orretaining shell it is possible to make the enclosed air chamber orcavity or any desired form, such as exponential, parabolic, etc., forexample, so as to reduce resonance and other objectionable effects.

Other objects of my invention will appear from the drawings and as thedescription proceeds.

Referring to the drawings:

Figure 1 is a perspective View of my radio easy chair carrying twospeakers, one near each ear of a listener, and of a console and separateloud speaker;

Figure 2 is a vertical axial sectional View, partly in elevation of aspeaker illustrating one embodiment of this part of my invention;

Figure 3 is a view somewhat similar to that of Figure 2 showing aconstruction in which the tube 28D has been bent downward to permit theuse of a large speaker, 3, without touching, or interfering with theshoulder of the listener;

Figure 4 is a View somewhat similar to that of Figure 2, but whichinvolves a different principle in the formation of the vibration-chamberand Vibration-restraining and directing wall or plate 3|;

Figure 5 is a View similar to that of Figure 2, but showing a furthermodification of the diaphragm and of the vibration chamber;

Figure 6 is a detailed vertical sectional view of one form of thedelivery end of the air chamber of one of my speakers, and of a flexibletip attached thereto;

Figure '7 (sheet 3) is a view somewhat similar to that of Figure 6, butshowing a much longer flexible tapering tip;

Figure 8 is a sectional view, on an enlarged scale, of the constructionshown at the lower right hand corner of Figure 3;

Figure 9 is a View partly in elevation and partly in section, of one ofmy speaker units especially adapted for contact with the side of thehead;

Figure 10 shows one manner of determining the contour of my special typeof horn or concentrator or concentrating and accelerating front plate;

Figure 11 is a detail view, partly in` section, of the diaphragm end ofthe tube which, with the diaphragm, forms the air chamber forward of thediaphragm and leads to the ears or ear of the listener.

Similar reference characters refer to similar parts in all the drawings.

Some of those reference characters, together with brief notation as tothe parts to which they refer, follow:

I Chair 2 Listener 3, 3 Speaker; 3a back shell; 3b supporting casting;3c horn 4, 4 Pipes for loud speaker 5 Console; 5a controls; 5b rotaryswitch; 5c

microphone 23 Insulating material inside 3a; 23a insulating lining of30; 23h ring between 33 and 25; 23e insulating ring, ring between 25 and21 and 3a; 23d insulating ring on top of 23C and 21 24 Speaker potSpeaker shell; 25a spring washer disc; 25h washer; 25o reinforcing anglefor shell 25 Diaphragm; 26a spider; 2Gb spacer Front plate; 21a ridge:on front plate Air passage or chamber; 28a orifice; 28D tube Concalfiller piece; 29a straight topped filler piece 30 Closure plate; 30aclamping ring; 30h bolts;

30C insulating tube around 3llb; 30d insulation between 30a and 30 3|Preferred type of front plate or concentrator 32 Soft rubber ear piece;32a thimble in 32;

32h bent flexible ear piece Speaker shell bracing and anchoring ring.

In the drawings, and particularly in Figure l, I indicates abody-supporting means for the listener, 2 who is to receive music orother sounds from the speakers, 3, 3, which are so carried by arms orsupports, 4, 4, extending from beneath the body supporting means, I,which is here shown as a chair, preferably a stuffed or easy chair, butwhich may be a couch, or a bed, or any other suitable means forsupporting the body of the listener, so that his head will be betweenthe speakers, 3, 3 whose orices are approximately opposite to, and inline with the openings of his ears.

5 (see Figure 1) indicates a console containing the principal parts ofthe set, except the loud speaker, and which carries on its top the usualcontrols, 5a, also my special controls, 5b and 5c. 5b is a switch, suchas a rotary switch, by which the amplified current from the set may bethrown either into the loud speaker, or to the speakers on the chair asdesired, or when desired, into both at the same time, by setting it onthe 1st, 2nd, or 3rd positions. The 4th, 5th, and 6th positions cut offthe radio signal and connect the microphone through the audio stages ofamplification of the set or, if desired, through a special amplifierseparate from the set, and also deliver the amplified microphone currentto the chair, the loud speaker, or both as desired. 5c is the microphonecurrent control.

Also, instead of horns expanding from a small end up to a much largerbell, I sometimes reverse this, and have the large end. down near thediaphragm, the tube gradually tapering up to a small end or ends closeto the ear or ears of the listener. See Fig. 11.

The speakers 3, 3, (see Figures 2 to 9) comprise an outer or back caseor shell 3a, here shown of concave form which is in shape somewhat likethe small end of an, egg, and having on, or against its interior surfacea thick lining of sound-insulating material 23, such as rubber, felt, orsponge rubber, though any other suitable insulation may be used. Withinthis outer shell is the speaker pot, 24, carried by a support or frame,25, constituting the speaker frame. In front of said frame 25 is a coneshaped vibrating diaphragm 26; and in front of this diaphragm is a frontplate, concentrator, accelerator, and intensifier, 21, so shaped as toform., between it and the diaphragm, a passage 28, of such form andproportions that it will accelerate, concentrate, intensify, and directthe vibra-tions of the air arising from the movements of the diaphragmtoward the small orifice 28a. In the constructions shown in Figures 2and 3, the diaphragm 25 has a central opening over the center pole ofthe magnet. Into this opening a spider, 26a, is secured. The centralportion of this spider is held fast between the spacer, 2Gb, attached tomagnet and filler piece, 29, Which is screwed fast to spacer 2Gb.

This filler piece 29 is somewhat conical in` form,

and of such size and shape as to form a passage,

28, near the central portion. of the diaphragm, of the constantlydecreasing area necessary for the smooth and continuous acceleration ofthe vibrations necessary for the proper concentration of sound at theorifice, 28a.

When the speaker unit 24, 25, and 26, with the front plate 21 or 3l asshown in Figs. 2, 3, 4, 5 and 8 has been put into the cases or shells,and they Ahave been, closed the result should be that insulating lining23 comes up tight under reinforcing ring 33. On top of ring 33 restsinsulating ring 23h. On top of 23h rests the rear peripheral surface ofspeaker frame 25, upon Whose upturned edge, and reinforcing angle 25e,rests rear peripheral portion of front plate 2l, or 3l. Outside of thesetwo between them and the shell 3a, is inserted insulating ring 23o,which is pressed down tight on 23h. On top of 27 and 23o restsinsulating ring 23d. On top of 23d rests rcar peripheral surface ofclosure plate 3l). On top of that rests insulating disc Washer or gasketStd. On top of 36d rests clamping ring Sta. All of these parts. are heldtightly together by the insulated screws or bolts 3th which are threadedinto ring 33. The bolts Stb, Sib, pass down through tubes 30o, 38e ofinsulating material, and hold all the above parts tightly together.

Inserted between the diaphragm, 26, and the frame or support, 25, is adisc washer 25a, of spring material, most of whose center has been cutaway. On front plate 21 is formed a rib or ridge, 21a, which holds thediaphragm, 26, tightly down on to the spring washer 25a, and so closesoff air chamber or passage 28.

In the speakers shown in Figures 6 and 7, the chamber or space, 28,between the diaphragm and the front plate, increases in depth, ordistance from diaphragm 26 to front plate 2l, to a point near the centerof the diaphragm, where it turns forward and forms a tube, 28h, ofgradually reducing diameter, which terminates in the orifice 28a.

The intent is that the area of the air chamber shall be of apredetermined form, such, for example, as that of the air chamber of anexponential horn, or one designed on my curve shown in Fig. 10. Theouter end of this tapering tube 28h is, in Figures 2, 3 and 6, shown asspaced away from the opening in closure plate 3E! by a sound-insulatingring 30h. An ear piece 32 of soft rubber, or the like, adapted to fitinto the outer opening of the ear of a listener, and attached to thetapering tube 28 by a sleeve or thimble, 32a, may sometimes be used whena louder effect in the ear of the listener is desired.

Figs. 4, and-9 show speakers with a front plate, 3|, quite differentfrom the type of front plate 21 previously described. In this type offront plate, the sides curve forward and inward from its periphery toits orifice at 28a. When this type of front plate is used in conjunctionwith my diaphragms shown in Fig. 5 no ller piece, 29, is needed. But ifthey are used in conjunction with ordinary diaphragms with a hole incenter, iiller piece 29a, Fig 4, which is flat on top, and which comesjust up to the edge of diaphragm, is necessary for best results. Thistype of front plate moves the air forward and accelerates it with verygreat smoothness, and without the danger of eddy currents or distortionswhich may occur in the other. In Figure 5 the diaphragm, 26, is of theinverted type, and terminates in a sharp point which extends forwardinto the throat of front plate 3|. The air chamber enclosed betweendiaphragm and front plate is of predetermined area.

Loud speakers are ordinarily so constructed as to set all of the air ina room into vibration so as to produce the sensation of sound throughoutthe entire room, as loudly or softly as may be desired. rIhe object ofmy invention is not to produce the sensation of sound throughout a roomor a house, but to so confine, concentrate and accelerate the movementof air produced by a diaphragm of large surface, and very smallamplitude of vibration, that it will produce a small stream or jet ofvibratory air of very much greater amplitude of vibration than theamplitude of vibration of the diaphragm which produced it. I thendeliver these streams of vibratory air close to the ears of thelistener. A sound vibration of quite small amplitude, if delivered closeto the ear, or better the ears of a listener, will ordinarily produceall the sensation of sound he desires. Therefore, these very smallstreams (frequently 1A or -even less in diameter) of small amplitudevibrations, emerging close to the ears of the listener, produce only anegligible sound in the rest of the room. For best and most quietresults, however, it is necessary to enclose the speaker in aninsulating shell, or an insulated shell, or case, as here shown, so as'to prevent vibrations, other than the useful vibrations from orifice28a, from escaping into the room.

In the construction shown in Figures 2 and 3, the air passage beginningat the peripheries of the diaphragm and front plate decreases incapacity at a predetermined rate, preferably that of an exponential hornfrom bell to small end, or on that of my curve shown in Fig. 1G. In theconstruction shown in Figure 2 the air passage extends from theperipheries of the diaphragm and front plate inward and rearward to nearthe centre, and then turns forward into tube 28h, the rate of decreaseat the turning into this tube being maintained by the conical fillerpiece 29. The tube 28 in Figure 2 extends directly forward from theturning, while in Figure 3, in` which the diaphragm and front plate arelarger than in Figure 2, the tube is bent downward to bring it into linewith the 4ear o1" the listener, so as to allow the bottom of the speakercase to clear the listeners shoulder.

The front plate 21, or 3i, is in effect a horn of the type known asexponential but reversed, that is, with the vibratory diaphragm at thelarge end, and of substantially the full diameter of that end, soconcentrating and accelerating all the air moved by the entire area ofthe diaphragm, and forcing it out through the orice 28a, which, in mostof my chairs, is almost microscopically small in comparison with thearea of the diaphragm.

rIhis horn, or concentrator, may be shaped on a curve which I have shownin Fig. l0. To lay out this curve I draw a line a-a to indicate thesmall end of the horn and a line b-b parallel with a-a to indicate theother or larger end. Perpendicular to these end lines, and midwaybetween their ends, I draw lines c-c and d-d spaced apart a distancecorresponding to the diameter of the opening at the small end of thehorn. On line b b" the distance between b and c is divided into adefinite number of equal spaces, and the distance between b and d isalso divided into the same number of equal spaces. Lines c-c and d-d areeach marked off for the same number of equal spaces as are lines b-c andb'-d, though the spaces so marked on on lines c-c and d-d' need not beand as shown are not equal to the spaces marked off on lines b-c andb-d. The number of divisions here indicated on lines c-c and d-d istwenty but may be more.

Lines are then drawn from the first division point at the outer end ofline bc to the first division point above line b-c on line c-c formingline I--I; from the second division point from the outer end of line b-cto the second division point on line c-c above line b-c forming line2-2, and so on to form a series of lines i-i, 2--2, etc., each drawnfrom a numbered point on a horizontal line to a correspondingly numberedpoint on a vertical line, and so on till all 20 lines have been drawn.Then complete the other side likewise. Each of these lines will crossmany of the other lines and the junction points on the outside of thefigure will give a curve which from the experience of many years, I havefound to give very satisfactory results acoustically both as a horn andas a concentrator.

In all of the forms of loud speakers shown, the interior of the shell islined throughout with insulating material, and the closure plate is alsolined throughout with insulating material, preferably rubber or spongerubber, and the front or closure plate is so cushioned at its peripherythat vibrations will not be transmitted from one to the other.

Figure 9 shows, partly in side view and partly in vertical centralsection, a completely-insulated speaker in which the rubber or spongerubber vibration deadener has been vulcanized on to the parts. The frontclosure plate, 30, is provided with an extension, 23h, adapted to t overthe ear of the listener. The recess for the ear in 23hl is made ofapproximately the size and shape of the human ear.

Fig. 11, which is a detail view, partly in section, shows a modification|85 of the tube, leading from the speaker, to which flexiblesoundconducting tubes may be secured. This, if formed of sheet metal, isto be covered, or lined, with a sound-insulating material |850..

From the foregoing description, and by reference to the drawings, forexample, Figs. 2 and 3 and particularly Figs. 4, 5 and 9, it will beapparent that novel principles of substantial utility are embodied inthe disclosed means. In my speakers, the enclosed chamber, which isdivided by the diaphragm into two parts, namely, the outer or upper partand the inner or lower part, serves as an infinite baie, since the airmoved forward by the diaphragm is prevented by the case or shell fromwhirling around and reaching the rear side of the diaphragm. Also thereis involved the important principle of utilizing two air chambers ofdissimilar sizes and dissimilar shapes, which are divided from eachother by the diaphragm and thus prevent resonances. The front plate maybe made on an exponential curve, or any other curve which may be formedto reduce resonances to the lowest point. The rear chamber formed by theshell and the insulating material is also designed with such a form asto give the least resonance possible. The insertion of the speaker frameand pot in this air chamber also tends greatly to reduce resonance andthe areas of the two chambers, that above or at the outer side of thediaphragm and that below or at the inner side of the diaphragm, are ofwidely differing contents, thus making the resonance points, if there beany, far apart, and so tending to work against each other, all of whichis further accentuated by the fact that the upper or outer air chamberis open to the outer air through an orifice such as 28a, whereas thelower or inner air chamber, that below the diaphragm, is completelyenclosed. The soft yielding insulating lining of the walls of the lowerchamber also tend greatly to reduce resonance. The results may befurther heightened by making the inside of the case, or of theinsulating material within the case, rough in form or suriace, so as toimpede the movement of air as much as possible. Where sponge rubber isused, this can be easily done by using a rough male mold when the spongerubber is vulcanized into the shell. Also, other screens or baffles maybe placed inside of the lower chamber further to impede any possibilityof resonances being set up.

My invention is not limited to the particular embodiments thereofillustrated and described herein, its scope being set forth in thefollowing claims.

Having thus described my invention what I claim is:

l. A sound reproducing device or speaker particularly adapted for thereception of sound by a single listener exclusively, comprising, incombination, a rear shell of substantially hemiellipsoidal form, aconical diaphragm having its periphery secured to the peripheral portionof said shell so as to provide a closed chamber rearwardiy of thediaphragm, actuating means for the diaphragm disposed axially at itsrear, means for concentrating, accelerating and intensifying the aerialvibrations at the front of the diaphragm and delivering them in arelatively small stream oi vibratory air close to the ear of a iistener,said means comprising a cone-like front plate having a conicalsound-delivery passage, said plate being attached peripherally to thespeaker shell adjacent the periphery of the diaphragm, said conicalsound-delivery passage forming between the front plate and the diaphragman air chamber of constantly decreasing area forwardly in planesperpendicular to the axis of the diaphragm, said conical sound deliverypassage terminating and opening outwardly at its plane of minimum area,and front cover means comprising a forwardly convex member connectedperipherally with the shell and having remote from its periphery anopening for the outward passage of the reduced portion of the frontplate.

2. A sound reproducing device or speaker particularly adapted for thereception of sound by a single listener exclusively, comprising, incombination, a rear shell of substantially hemiellipsoidal form, aconical diaphragm having its periphery secured to the peripheral portionof said shell so as to provide a closed chamber rearwardly of thediaphragm, actuating means for the diaphragm disposed axially at itsrear, means for concentrating, accelerating and intensifying the aerialvibrations at the front of the diaphragm and delivering them in arelatively small stream of vibratory air close to the ear of a listener,said means comprising a cone-like front plate having a conicalsound-delivery passage, said plate being attached peripherally to thespeaker shell adjacent the periphery of the diaphragm, said conicalsound-delivery passage forming between the front plate and the diaphragman air chamber of constantly decreasing area forwardly in planesperpendicular to the axis of the diaphragm, said conical sounddeliverypassage terminating and opening out- Wardlyat its plane of minimum area,and front cover means comprising a forwardly convex member connectedperipherally With the shell and having remote from its periphery anopening for the outward passage of the reduced portion of the frontplate, said shell and said cover means having sound-insulating meansover substantially their entire inner surfaces.

3. A sound reproducing device or speaker particularly adapted for thereception of sound by a single listener exclusively, comprising, incombination, a rear shell of substantially hemiellipsoidal form, aconical diaphragm having its periphery secured to the peripheral portionof said shell so as to provide a closed chamber rearwardly of thediaphragm, actuating means for the diaphragm disposed axially at itsrear, means for concentrating, accelerating and intensifying ther aerialvibrations at the front of the diaphragm and delivering them in arelatively small stream of vibratory air close to the ear of a listener,saidmeans comprising a cone-like front plate having a conicalsound-delivery passage, said plate being attached peripherally to thespeaker shell adjacent the periphery of the diaphragm, said conicalsound-delivery passage forming between the front plate and the diaphragman air chamber of constantly decreasing area forwardly in planesperpendicular to the axis of the diaphragm, said conical sounddeliverypassage terminating and opening out- Wardly at its plane of minimumarea, and means at the front of the speaker providing an opening for theoutward passage of the reduced portion of the front plate.

4. A sound reproducing device or speaker particularly adapted for thereception of sound by a single listener exclusively, comprising, incombination, a rear shell of substantially hemiellipsoidal form, aconical diaphragm having its periphery secured to the peripheral portionof said shell so as to provide a closed chamber rearwardly of thediaphragm, actuating means for the diaphragm disposed axially at itsrear, and means for concentrating, accelerating and intensifying theaerial vibrations at the front of the diaphragm and delivering them in arelatively small stream of vibratory air close to the ear of a listener,said means comprising a conelike front plate having a conicalsound-delivery passage, said plate being attached peripherally to thespeaker shell adjacent the periphery of the diaphragm, said conicalsound-delivery passage forming between the front plate and the diaphragman air chamber of constantly decreasing area forwardly in planesperpendicular to the axis of the diaphragm and terminating and openingoutwardly at its plane of minimum area.

ARTHUR T. CAHILL.

